// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_
#define UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_

#include "base/compiler_specific.h"
#include "base/macros.h"
#include "ui/views/view.h"
#include "ui/views/views_export.h"

namespace views {

class ScrollBar;

/////////////////////////////////////////////////////////////////////////////
//
// ScrollBarController
//
// ScrollBarController defines the method that should be implemented to
// receive notification from a scrollbar
//
/////////////////////////////////////////////////////////////////////////////
class VIEWS_EXPORT ScrollBarController {
public:
    // Invoked by the scrollbar when the scrolling position changes
    // This method typically implements the actual scrolling.
    //
    // The provided position is expressed in pixels. It is the new X or Y
    // position which is in the GetMinPosition() / GetMaxPosition range.
    virtual void ScrollToPosition(ScrollBar* source, int position) = 0;

    // Returns the amount to scroll. The amount to scroll may be requested in
    // two different amounts. If is_page is true the 'page scroll' amount is
    // requested. The page scroll amount typically corresponds to the
    // visual size of the view. If is_page is false, the 'line scroll' amount
    // is being requested. The line scroll amount typically corresponds to the
    // size of one row/column.
    //
    // The return value should always be positive. A value <= 0 results in
    // scrolling by a fixed amount.
    virtual int GetScrollIncrement(ScrollBar* source,
        bool is_page,
        bool is_positive)
        = 0;
};

/////////////////////////////////////////////////////////////////////////////
//
// ScrollBar
//
// A View subclass to wrap to implement a ScrollBar. Our current windows
// version simply wraps a native windows scrollbar.
//
// A scrollbar is either horizontal or vertical
//
/////////////////////////////////////////////////////////////////////////////
class VIEWS_EXPORT ScrollBar : public View {
public:
    ~ScrollBar() override;

    // Overridden from View:
    void GetAccessibleState(ui::AXViewState* state) override;

    // Returns whether this scrollbar is horizontal.
    bool IsHorizontal() const;

    void set_controller(ScrollBarController* controller)
    {
        controller_ = controller;
    }
    ScrollBarController* controller() const { return controller_; }

    // Update the scrollbar appearance given a viewport size, content size and
    // current position
    virtual void Update(int viewport_size, int content_size, int current_pos);

    // Returns the max and min positions.
    int GetMaxPosition() const;
    int GetMinPosition() const;

    // Returns the position of the scrollbar.
    virtual int GetPosition() const = 0;

    // Get the width or height of this scrollbar, for use in layout calculations.
    // For a vertical scrollbar, this is the width of the scrollbar, likewise it
    // is the height for a horizontal scrollbar.
    virtual int GetLayoutSize() const = 0;

    // Get the width or height for this scrollbar which overlaps with the content.
    // Default is 0.
    virtual int GetContentOverlapSize() const;

    virtual void OnMouseEnteredScrollView(const ui::MouseEvent& event);
    virtual void OnMouseExitedScrollView(const ui::MouseEvent& event);

protected:
    // Create new scrollbar, either horizontal or vertical. These are protected
    // since you need to be creating either a NativeScrollBar or a
    // ImageScrollBar.
    explicit ScrollBar(bool is_horiz);

private:
    const bool is_horiz_;

    ScrollBarController* controller_;

    int max_pos_;

    DISALLOW_COPY_AND_ASSIGN(ScrollBar);
};

} // namespace views

#endif // UI_VIEWS_CONTROLS_SCROLLBAR_SCROLL_BAR_H_
